Conventionally, in an automotive air conditioner, the driving force of an automotive engine has been used to drive a compressor for compressing a refrigerant. However, with the recent practical use of electric vehicles and the like, what is called an electric compressor, in which an electric motor is used as a driving source for the compressor, has been developed.
In such an electric compressor, since the driving torque produced by the motor is lower than that produced by an engine, if the pressure difference of refrigerant between the inlet side and the outlet side of the compressor is large especially at the time of actuation, there is a possibility that the compressor cannot be actuated. The reason for this is that the motor load that tends to actuate the compressor becomes excessive because of the large pressure difference, so that, in a motor drive control circuit, an overcurrent protecting function for protecting the motor is triggered.
To solve this problem, a technique has been proposed that there is provided a differential pressure sensor for detecting the pressure difference between the inlet side and the outlet side of the compressor, and a threshold value for judging whether or not the current flowing in the motor when the compressor is actuated is changed according to the detection value of the differential pressure sensor, or a voltage applied to the motor is controlled (for example, refer to Patent Document 1).
Patent Document 1: Japanese Patent Laid-Open No. 2006-29342